The present invention relates to a glass lens array module and a manufacturing method thereof, especially to a glass lens array module formed by precision assembling of a plurality of glass lens arrays and applied to lenses of LED sources, lenses of solar energy conversion systems, and optical lenses of mobile phones.
Glass precision molding technology has been widely applied to manufacture aspherical molded glass lens with high resolution, good stability and low cost such as lens revealed in US2006/0107695, US2007/0043463, TW095101830, TW095133807, and JP63-295448 etc. A glass preform (or glass material) is set into a mold cavity formed by an upper mold and a lower mold so as to be heating and softening. Then the upper mold and the lower mold are clamped correspondingly and apply pressure on the upper mold and the lower mold so as to make the soft glass perform have the transformed optical surfaces as that of the upper mold and the lower mold. After cooling, a molded glass lens with molding surfaces of the upper mold and the lower mold is produced. In order to reduce manufacturing cost, prior arts—JP63-304201 and US2005/041215 reveal a lens array formed by glass molding. As to a single lens-called a lens element hereunder, JP02-044033 revealed that a lens blank having a plurality of lenses is manufactured by movement of glass materials and multiple molding procedures. Then the lens array is cut into a plurality of lens elements.
The optical lens formed by glass molding is widely applied to assembled lenses of LED light sources, lenses of solar energy conversion systems, and optical lenses of mobile phone cameras with advanced features. The assembled lens or optical lens is formed by a plurality of optical lenses with different lens power arranged with a certain air gap between one another on the optical axis. Thus while assembling, an optical axis of each optical lens must be aligned precisely so as to avoid the reduction of resolution, so called optical precision assembling, rather than the mechanical precision. Moreover, the distance between two adjacent optical lenses (interval of air gap) is fixed. Thus the assembling requires a complicated processes and precise calibration process. Therefore, the yield rate is unable to increase and the cost down is difficult. Since the optical resolution (example as MTF effect) will be affected when the optical assembly having disalignment from optical axis, the lens alignment of the optical lenses is more complicated and important.
As to the manufacturing of the optical lens array, JP2001194508 disclosed a manufacturing method of plastic optical lens array. Taiwanese patent No. M343166 reveals a manufacturing method of glass optical lens array. After being produced, the optical lens array can be cut to form a single optical lens element so as to be assembled in a lens module. Or the optical lens array is assembled with other optical elements to form a lens submodule array that is then cut to form a lens submodule. The lens submodule is assembled with lens holder, image sensors (image capture devices) or other optical elements to form a lens module. In manufacturing of lens module array, wafer level lens modules are revealed in U.S. Pat. No. 7,183,643, US2007/0070511, WO2008011003 and so on. Refer to FIG. 1, a lens module array generally includes an aperture 711, a cover glass 712, a plurality of optical lenses and an infrared (IR) cut lens 717. As shown in figure, the plurality of optical lenses forms a three piece type optical lens set. The optical lens set includes a first optical lens 714, a second optical lens 715 and a third optical lens 716. Two adjacent optical lenses are separated by a spacer 713. After being assembled, a lens module array is formed and then is cut into a plurality of lens modules.
In a lens module array, while assembling a lens array with plurality of optical lenses, the alignment of the lens array has effects on resolution of the lens module. In US2006/0249859, imaging techniques are used to determine if stacked wafers are in proper alignment. Fiducial marks that were previously patterned on each wafer of the stack are exposed in an image produced by the infrared ray. In assembling of plastic optical lens arrays, JP2000-321526 and JP2000-227505 revealed bi-convex type optical lens arrays formed by combination of heights with crevices. As to U.S. Pat. No. 7,187,501, cone-shaped projections are provided on a periphery of a resin lens. A plastic lens array is formed by stacking the resin lens plates one over another through fitting these projections and holes to each other. However, in the conventional assembling way of projections and holes to form plastic optical lens array, material shrinkage after the plastic injection molding will lead to size change (or alignment change) of the projections and the holes. Thus the location precision is affected and the alignment of the optical axis is difficult. Therefore, the applications of the plastic optical lens array is limited, especially during manufacturing of small-size lens module, the complicated processes cause cost increase. The molded glass lens has higher refractive index than the plastic lens and also with better thermostability so that the molded glass has been applied to various optical systems. Moreover, the optical lens array made from molded glass exhibit less shrinkage.
Thus there is a need to develop a method of manufacturing stacked optical glass lens arrays as well as stacked lens modules with simple structure and high precision so as to provide stacked lens modules for assembled lenses of light emitting diode (LED) light sources, assembled lenses of solar energy conversion systems and optical lenses of phone cameras. And the lens modules meet requirements of mass-production and yield rate.